[PATCH v2] ARM: imx: Fix suspend/resume crash with Clang CFI

[Yo'av Moshe <linux@yoavmoshe.com>]

Relocated suspend code in OCRAM lacks compiler-generated CFI type
signatures. When CONFIG_CFI=y is active, the indirect call to
imx6_suspend_in_ocram_fn triggers a strict CFI violation panic.

Annotate imx6q_suspend_finish with __nocfi to bypass CFI checking
for this specific indirect call.

Additionally, protect the imx6_suspend_in_ocram_fn pointer by marking
it __ro_after_init to prevent it from being used as a CFI bypass
exploit vector.

Cc: stable@vger.kernel.org
Signed-off-by: Yo'av Moshe <linux@yoavmoshe.com>
---
Tested on a Kobo Clara HD (i.MX6SLL SoC) running postmarketOS edge. 
Before this patch, suspending the device caused an immediate silent 
hang requiring a hard-reboot. With this patch applied, suspend and 
resume work successfully.

Differences from v1:
- Added __ro_after_init to imx6_suspend_in_ocram_fn to prevent it
  from being exploited as a CFI bypass gadget.

 arch/arm/mach-imx/pm-imx6.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mach-imx/pm-imx6.c b/arch/arm/mach-imx/pm-imx6.c
index a671ca498..b425a4701 100644
--- a/arch/arm/mach-imx/pm-imx6.c
+++ b/arch/arm/mach-imx/pm-imx6.c
@@ -63,7 +63,7 @@
 
 static void __iomem *ccm_base;
 static void __iomem *suspend_ocram_base;
-static void (*imx6_suspend_in_ocram_fn)(void __iomem *ocram_vbase);
+static void (*imx6_suspend_in_ocram_fn)(void __iomem *ocram_vbase) __ro_after_init;
 
 /*
  * suspend ocram space layout:
@@ -360,7 +360,7 @@ int imx6_set_lpm(enum mxc_cpu_pwr_mode mode)
 	return 0;
 }
 
-static int imx6q_suspend_finish(unsigned long val)
+static int __nocfi imx6q_suspend_finish(unsigned long val)
 {
 	if (!imx6_suspend_in_ocram_fn) {
 		cpu_do_idle();
-- 
2.55.0